[GRASS-user] Problem with slope modeling .

[Amaginary Studios]

I was looking at your image you linked too of your DEM with slope  
profile.

I am really confused by your Isolines....

The profile you drew on your DEM shows exactly what you would expect  
from your transect along the DEM colour sensitive elevations.

The Isolines however are completely contradictory.... but... Maybe  
these isolines are for something entirely else besides elevation?

Sorry, can't wrap my head around what those isolines are representing...

When you say:

> I expect that the slope between two isolines on the bottom of the  
> valley will be similar.

I presume the Isolines are representative of Elevation.

If the Isolines are representative of Elevation then what is the DEM  
representative of?

Your profile is of your Raster image, and your transect profile along  
that image shows a fairly constant elevation with the slight dips  
that are represented in your Profile graph.
Meanwhile the isolines are telling a completely different story....

Is there any chance that one of your fields inputted was mixed up  
between slope and elevation, that your DEM is perhaps incorrect?
I am used to seeing similar colours ALONG the length of the Isolines  
not Against them.

Maybe I'm way out in left field picking daisies... I don't know...

Nice snapshot thought!

good luck!

Mars

On 24-Mar-07, at 1:03 PM, Radomir wrote:

> Hi all,
> I'm preparing the slope and elevation map from digitised isolines.
> I'm using v.surf.rst to do that with the following options:
>
> v.surf.rst input="izolinie_punkty" layer=1 zcolumn="wysokosc_m_npm"
> dmax=3.174812 dmin=0.634962 elev="mapa_wystaw" slope="mapa_spadk"
> maskmap="maska" zmult=1.0 tension=40. segmax=40 npmin=300
>
> The screenshot from small part of resulting map is here:
> http://mort.no-ip.org/screen.png
>
>
> On this screen you can see the valley in the center. I expect that the
> slope between two isolines on the bottom of the valley will be  
> similar.
> But it is changing and gives an effect of "wave" between isolines.  
> Those
> "waves" cause the unexpected results in LS factor.
>
> I was trying to manipulate with the tension and smoothness but without
> visible results.
>
> What should I change to calculate better slope model?? Any help with
> understanding will be appreciated.
>
> Best Regards,
> Radomir
>
>
>
> -- 
> Radomir
>
> ----
> The Future Is Now ;)
>
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Amaginary Studios
amagine at telus.net
Phone 250 845 7999

Mars Sjoden
3320 Mount Davis Way
Houston BC
V0J 1Z2

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